The present invention relates to an improved magnetic recording tape or, in particular, to a magnetic recording tape free from the problems due to the accumulation of static electricity.
Needless to say, magnetic recording tapes are widely used in various fields of electronics technology including audio tapes, video tapes, computer tapes and the like. Since almost all of the magnetic recording tapes currently on use are formed with a film base of a synthetic plastic resin coated on one surface with a magnetic composition, they have problems due to the electrostatic charging. That is, among the plastic materials used for the film base of the magnetic recording tapes such as polyesters, polyvinyl chlorides, cellulose acetates and the like, polyester-based ones are generally preferred by virtue of the large mechanical strengths thereof over the other kinds of the plastic materials in accordance with the recent requirement for a thinner and thinner film base to reduce the volume of the tape roll. Polyester-based film base for the magnetic recording tapes, however, is very susceptible to the accumulation of static electricity thereon so that the magnetic recording tapes with the polyester film base are unavoidably defective due to the static electricity such as the variation of the travelling velocity in recording and playing, generation of noise when used in sound recording, disorder in the picture images when used in video recording, distortion of the roll form and the like.
Of course, there have been made various attempts to prevent such disadvantageous phenomena by improving the antistatic property of the magnetic recording tapes to be less susceptible to the electrostatic charging. One of the approaches is the incorporation of an electroconductive filler such as carbon black into the plastic film as the film base for the magnetic recording tape. The other approach is the use of an antistatic agent which is either incorporated into the plastic film by blending or used for coating the surface of the film base. The former method has problems in the decreased smoothness of the surface of the tape and lower mechanical strengths thereof since sufficient antistatic effect can be obtained only by the incorporation of a considerably large volume of the carbon black. The latter method of the use of an antistatic agent is also not free from problems in that the durability of the antistatic effect obtained therewith is relatively low and further the antistatic agent bleeding on the surface of the film base sometimes transfers to the magnetic layer when the magnetic recording tape is wound to make up a roll so that adverse effects are caused on the sounds and picture images when the tape is played.
Accordingly there has been an eager demand for developing a method in which improvements can be obtained in the antistatic performance of a magnetic recording tape without the above mentioned problems in the prior art.